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[ph10west]

I have a Taco 560 three way bypass valve. If I throw the manual lever it will open the valve partially to the heat exchanger.  But does not open all the way and the flow to the waterheater is easier since the heatexchanger is overhead. I tried to steal power from my radiant floor pump but the valve stayed all the way closed. I'm going to get a transformer and see if that will work. 

[RSI]

I have a Taco 560 three way bypass valve. If I throw the manual lever it will open the valve partially to the heat exchanger.  But does not open all the way and the flow to the waterheater is easier since the heatexchanger is overhead. I tried to steal power from my radiant floor pump but the valve stayed all the way closed. I'm going to get a transformer and see if that will work.

I hope you didn't connect it to 120v. If you did, it should have smoked pretty good.
You need 24 volts AC to run it.
Do you want it to open when the blower runs?

[ph10west]

No, Not 120V. I metered the termnal block on the zone pump and found ~28v.  Thought that would be close enough.  Yes I want it to open when the fan runs.

[RSI]

I am not sure if a relay coil between the C and G wires would be enough to turn the fan on so this is how I would do it to make sure it doesn't.
Get a 2 pole relay with 24v coil. Connect one side of the coil to the R terminal in the furnace. Cut the G wire at the furnace and connect the side that is going to the thermostat to the other side of the coil. Connect the other side of the cut wire to the normally open contact of one of the poles (if you have a DPDT relay)
Then run a wire from the R to the  terminal in the furnace to the common contact for that pole.
Then get a 24v transformer and connect one side of the 24v to the zone valve and the other wire to the common of other pole of the relay.  Connect one of the wires of the zone valve to the normally open and the other wire to the other wire on the transformer. You will also have to connect the primary of the transformer to 120v AC.

[ph10west]

Follow-up... I ended up using Relays and switches.  I have a light switch to turn on/off constant power to the 3-way valve so I can have a spring/fall or day mode. In winter or night mode I have constant flow to the ductwork heat-exchanger. There are two sets of wires coming from the transformer to the valve(one is the thru the manual switch, the other goes thru the relay. In the spring/fall mode my first relay allows (With the switch off) the hot water only to flow the heat-exchanger in my ductwork when the relay (Normally closed) is tripped by the 2ndary t'stat.   This will keep from heating the air when I am trying to cool and keep the convective heat from coming from the ducts with the heat off.  I got to take the panel off my air-handler and see exactly what my heating and air guy did with the other relay to break the signal that feeds back thru the primary t'stat and allow the heatpump and a/c to work normally.